1. Technical Field
This disclosure relates to a particle counter for chemical solution.
2. Related Art
In the manufacture of semiconductor wafers, the improvement of yields is an important issue. In this regard, impurity particles included in a chemical solution affect manufacturing processes. ITRS (International Technology Roadmap for Semiconductors) specifies the size of particles to be controlled in a chemical solution. Accordingly, it can be checked whether the chemical solution meets the standards by counting the particles in the chemical solution.
A particle counter is provided as a device for measuring particles in a chemical solution at relatively low cost. At the particle counter, the flowing chemical solution is irradiated with laser light. Then, scattered light from the particles in the irradiated flowing chemical solution is observed to count the particles.
However, the chemical solution also scatters laser light. Thus, in the case of measuring particles in a chemical solution, larger background noise occurs as compared to the case of measuring particles in the water. Accordingly, some particle counter is improved in the SN ratio by attenuating a high-frequency component resulting from background noise included in a detection signal (for example, see JP-A-2014-92507).